The present invention relates generally to a plug for sealing against contamination, and more particularly, to a plug configured to sealingly engage within an acme nut of a QCC-1 coupling when the nut is disengaged from a propane cylinder collar.
Newer style gas grills typically include a standardized coupling commonly referred to as a QCC-1 coupling. In this coupling, the outlet collar of a propane cylinder includes an external right hand acme thread, and the end fitting that couples the cylinder to a pressure regulator or hose leading to the grill includes a large, hand-operable nut rotatably mounted on an elongate nipple of the type used in a POL coupling. Engagement of the internal acme thread on the nut with the external acme thread on the outlet collar axially slides the nipple into the inlet, thereby pushing open a self-closing metal diaphragm and allowing gas to flow therethrough. These simultaneous actions require dimensions measured from a datum point of a notional final contact and closure of the acme threads in the nut.
When the nut and collar are disengaged, it is possible for coarse particles and contamination to enter the nut, hose and regulator, thereby restricting gas flow. In coastal areas in particular, finer contaminants and atmospheres can further dissolve out the zinc from the brass alloy of the nipple, resulting in microscopic pitting of the surface of the remaining copper and degrading the sealing ability of the coupling assembly.
Accordingly, it would be desirable to seal the coupling system against contamination when the nut and collar are disengaged.